Former IMF chief Dominique Strauss-Kahn faced a potential new sexual assault investigation after a young French writer said she would formally accuse him of trying to rape her during a 2002 interview.

With France debating Mr Strauss-Kahn's possible return to presidential politics, he hit back at author Tristane Banon's plans to take him to court, calling her account "imaginary" and saying he planned to file a criminal complaint of slander.

The sordid exchange may have deep ramifications for the 2012 presidential race in France, where the surprise weakening of the sexual assault case against Mr Strauss-Kahn in New York last week sparked a fierce debate about whether he should return to politics if the American case against him collapsed completely.

Mr Strauss-Kahn was arrested in New York in May, accused to rape a hotel maid. He denied wrongdoing and was released without bail last week after questions emerged about the maid's credibility.

Before Ms Banon's announcement, polls showed voters were evenly split about whether Mr Strauss-Kahn, 62, should try to revive a career that until recently had him on track to take on conservative president Nicolas Sarkozy in the race to be France's next leader.

Mr Strauss-Kahn has been living under house arrest in a £31,000-a-month town house in the trendy TriBeCa neighbourhood. Once released, Mr Strauss-Kahn had dinner at a plush Manhattan restaurant.

"To see Strauss-Kahn freed then straight away eat in a luxury restaurant with friends, that makes me sick," Ms Banon told the magazine L'Express in an account published yesterday.

"I only want one thing, that he comes back to France, with his presumption of innocence, so that we can go before a court."

Ms Banon, 31, said on a 2007 television show that she had been attacked five years earlier by a politician she had interviewed for a book in his apartment. She later identified the man as Mr Strauss-Kahn.

"It finished very violently," she said on the television show. "I kicked him. He opened my bra. He tried to undo my jeans. It finished very badly."

Lawyer David Koubbi said Ms Banon had been dissuaded from filing charges by her mother, a regional councillor in Mr Strauss-Kahn's Socialist party.

Her mother, Anne Mansouret, admitted in a French television interview in May that she had urged her daughter not to file a complaint after the incident.

Ms Banon came forward again after Mr Strauss-Kahn's May 14 arrest in New York, but Mr Koubbi said his client had no intention of pressing charges while the American prosecution was going on because the two cases should be kept separate.

Ms Banon is now moving forward, Mr Koubbi said.

Mr Strauss-Kahn's lawyers said Mr Strauss-Kahn "has always said that the incident described by Ms Banon since 2007 is imaginary".

"He notes that this complaint comes quite conveniently right at the moment when there is no longer the slightest doubt about the false nature of the accusations against him in the United States," lawyers Henri Leclerc and Frederique Baulieu said in a joint statement.

Mr Strauss-Kahn has relinquished his passport to authorities in New York. Another court hearing would be needed for him to get it back.

His next appearance is scheduled for July 18 - five days after the deadline for candidates to register in the Socialist Party primary.